Roller mill



June 4, 1957 E; P. PETERS 2,794,603

ROLLER MILL s Sheets-Sheet 1 Filed NOV. 24, 1953 4 I 3110mm E2 M5? 2 257595 (Ittpmeg United States PatentO Machine Works, Inc Brooklyn, N. Y., a corporation of New York Application November 24, 1953, Serial No. 94,129 4 Claims. (0. 241-231 This invention relates to roller mills of the type used for grinding paint, ink, chocolate and materials having similar characteristics, and has foi an object to provide a roller mill having novel and improved details of construction and features of operation.

Another Object is to provide, in a roller mill having hydraulic means for adjusting the pressure on the rolls, novel and improved means for recharging the hydraulic cylinder so as to maintain the desired hydraulic 'piessurc.

Another object is to provide a novel method and means for operating a roller mill so as to improve the grinding efficiency thereof.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed;

The novel features which are chafacteris'tic of the present invention will be better understood by referring to the following description, taken in connection with the accompanying drawings forming a part thereof in which a specific embodiment has been set forth for purposes of illustration.

In the drawings:

Fig. l is a top plan view of a three-roll 'r'oller mill embodying the present invention, with parts in section to show the construction thereof;

Fig. 2 is a vertical transverse section taken on the line 22 of Fig. 1;

Fig. 3 is a side elevation of the roller mill of Fig. 1;

Fig. 4 is a detail view partly in section of a modified roller mounting;

Fig. 5 is a detail view on a larger scale showing the hydraulic system for applying pressure to the rolls;

Fig. 6 is a detail view similar to Fig. 5 showing the hydraulic system with the cylinder retracted; and

Fig. 7 is a partial detail view illustrating the operation of the grinding rolls.

Referring to the drawing more in detail, the rolter mill is shown as comprising a frame having upper and lower bearing plates 10 and 11 disposed on each side of the frame to receive bearing blocks 13, 14 and 15 therebetween. The bearing plates 10 and 11 are spaced by blocks 12 and are secured together by transverse channel members 18 and 19 to form a unitary frame structure.

The upper and lower bearing plates Iii and 11 are formed with channels 20 in which the bearing blocks 13, 14 and 15 are adapted to slide. In the embodiment shown in Figs. 1, 2 and 3 the center bearing blocks 14 are fixed to the plates 10 and 11 by suitable means and the back and front bearing blocks 13 and 15, respectivel'y are mounted to slide with respect thereto. Blocks 13 and 15 are normally held in retracted position by springs 21 and 22.

A back roll 25, a center roll 26, and a front roll 27 are provided with shafts 28, 29 and 30 respectively which are mounted in suitable bearings in bearing blocks 13, 14 and 15, respectively. The shafts 28, 29 and 30 carry meshing gears 31, 32 and 33 having teeth which are sulfismall movement between rolls which is effected during adjustment and use thereof. One of the shafts, shown on the drawings as shaft 28, is provided with a sprocket 34 which is driven by a chain 35 from a sprocket 36 mounted on the shaft 37 of a driving motor 38. It is to be understood of course that the drive from the motor 38 may be applied to anyone of the shafts 28, 29 and 30, or if desired the shafts may be separately driven by individual motors in which case the spur gears 31, 32 and 33 may be omitted.

A feed hopper for the material to be ground is shown as comprising end plates 40 which are attached to the frame of the machine by any suitable means and removable side plates 41 which extend between the end plates 40 and provide side closures. The layer of ground material is removed from the front roll 27 by means of an apron 42 having an edge 43 which bears against the front roll 27, and having side flanges 44 tapering toward a discharge opening 45.

In the embodiments shown in Figs. 1, 2 and 3 the bearings blocks 14 supporting the center roll 26 are rigidly attached to the bearing plates 16 and 11 by suitable means,

ci'ently deep to remain in mesh during the relativeiy not shown, and the bearing blocks 13 and 15 are independent-1y adjustable with respect thereto by hydraulic adjusting means which is shown more in detail in Figs. 5 and '6.

Referring to Figs. 5 and 6 the adjusting means comprises an extension 47 of the bearing block 13 and is provided with a vertical bore in which a cylinder 55} is rotatably mounted. The cylinder 56 is provided with a that surface 51 against which the end of a shaft 52 bears. The shaft 52 is loosely pinned by a pin 53 to a boss 54 of the extension 47, in the bearing block 13 so as to prevent separation of the parts, but at the same time to provide suflicient clearance to permitaxial movement of the shaft 52. The shaft 52 extends through an end closure 55 and is secured to a piston 56 sliding in a cylinder 57. The cylinder 57 is slidably mounted in a housing 58 integral with the block 12 and attached to the bearing plates 10 and 11 by bolts 59 and 60. Bolt 61 mounted in plate 11 serves as a stop to limit the retraction of the bearing block 13 and therefore the separation of the rolls 25 and 26. Adjustable bolt 62 serves as a stop to limit the advance of the cylinder 57 to the left as viewed in Fig. 5.

The cylinder 57 is adjusted axially by means of a shaft 65 which is threaded into a bore 66 of the cylinder 57, extends axially through an end cap 67 attached to the housing 58, and is provided with a hand Wheel 70 for purposes of adjustment. A thrust bearing 71 is provided within the end cap 67 to receive the end thrust of the shaft 65 due to the hydraulic pressure which is exerted upon the piston 56. Pressure gauge 75 is attached to the cylinder with the high pressure chamber 72 in advance of the piston 56 through a passage 76 in the end wall 77 of the cylinder, to register the liquid pressure acting upon the piston. A reservoir 80 containing hydraulic liquid is attached to the cylinder wall 57 and communicates through a passage 81 with the cylinder 57 in back of the piston 56 so as to permit the return to the reservoir 80' of any liquid which leaks past the piston 56 from the high pressure chamber 72. The passage 81 also communicates through a port 83 with the high pressure chamher 72 in the cylinder 57. The port 83 is closed by the piston 56 when the cylinder is advanced during the normal operation of the well as shown in Fig. 5, but is opened when the cylinder 57 is retracted as shown in Fig. 6.

The adjusting means is operated by applying suitable pressure to the hand wheel 70 so as to advance the cylinder 57 (to the left of Figs. 5 and 6), thereby exerting pressure upon the liquid in the high pressure chamber 72 which pressure acts upon the piston 56 to Preduc'e axial thrust which is transmitted through the rod 52 and cylinder 50 to the bearing block. The amount of pressure thus exerted is registered on the gauge 75.

The hydraulic adjusting means of Figs. and 6 is repeated for each of the bearing blocks 13 and 15. In normal operation the two hand wheel associated with the bearing blocks 13 at opposite ends of the back roll 25 are adjusted individually as above described until the desired pressure is exerted upon the roll 25 as indicated by the respective gauges 75. The two hand wheels associated with the bearing blocks 15 on opposite ends of 'the front roll 27 are similarly adjusted. During the grinding operation simple inspection of the four gauges 75 indicates whether the adjustment is being properly maintained.

When the adjustment is to be released, as for example at the end of a run, or should the one or more of the gauges indicate a loss of pressure, the corresponding cylinder 57 is retracted by actuation of its hand wheel 70 so as to bring the port 83 beyond the piston 56. When this adjustment is made any liquid which has passed the piston 56 is forced back into the reservoir 39 through the passage 81, and the reduced pressure in the chamber 72 causes liquid to be drawn from the reservoir 89 through the passage 81 and port 83 to recharge the chamber 72.

The chamber 72 may thus be refilled automatically whenever necessary by retracting the cylinder 57 as above described. If the cylinder is thus retracted as a routine operation at the end of its run prior to adjusting the same so as to set up the desired pressure for the following run, the cylinder will remain charged indefinitely. The necessity of interrupting the grinding operation to recharge the cylinder is thus avoided.

In the embodiment shown in Fig. 4 the construction is generally similar to that above described with the exception that in this embodiment the bearing blocks 13 carrying the back roller 25 are fixed to the bearing plates, the bearing blocks 14 carrying the center roller 26 are free to slide in the bearing plates and 11 and the bearing blocks carrying the front roller 27 are adjustably mounted as above described. In this embodiment the hydraulic pressure is applied only to the front roll 27 and the pressure is transferred from the front roll 27 to the center roll 2s which is thus caused to exert the desired pressure against the fixed back roll 25. Obviously the structure can be reversed and the front roll 27 fixed to the frame and the adjustment applied to the back roll if desired.

In the operation of this grinding rniil the material 90 to be ground is applied to the hopper as indicated in Fig. 7. The pressure between the rolls 25 and 26 prevents the material from passing therebetween. However, the rotation of the rolls causes a film of the material to be picked up and carried between the tons to form a layer 91 on the roll 26 and a layer 92 on the roll 25. The layer 91 on the roll 26 is transferred to the front roll 27 and thence to the apron 42.

The thickness of the layer 91 on the roll 26 and the fineness of the grind which is obtained are dependent upon the nature of the material, the pressure exerted by the rolls, and the relative speeds of the rolls.

As a feature of the present invention I have found that the thickness of the layer 91 on the center rolls 26 may be greatly reduced andthe fineness of grind correspondingly increased by making the back roll 25 rotate at a peripheral speed at least twice that of the center roll 26, and preferably three times that of the center roll 26. I attribute this effect to the wiping action of the back roll 25 when thus driven at a higher rate of speed, which wipe the excess material from the film 9'1 and causes the same to spread out in a thin layer on the roll 26. 'Any excess material thus removed in the film 92 on the back roll 25 is of course returned to the material 90 in the feexi hopper as the roll 25 completes its .rotatiop.

I have further found that in order to complete the above action the front roll 27 should be driven at a peripheral speed comparable to that of the back roll 25 although the speed of the front roll 27 may vary somewhat from the speed of the back roll 25 depending upon the characteristics of the grind. The rapidly rotating front roll then serves to remove the film from the center roll 27 at a rapid rate and further reduces the thickness of the film and increases correspondingly the fineness of the grind.

I have found that by using speed ratios for the rolls 25, 26 and 27 of the order of 3:1:3 a fineness of grind is obtained in one pass through the grinding mill which is at least equivalent to the grind obtained by several passes when using more conventional speed ratios.

As another advantage of the present invention the desired fineness of grind may be obtained while using less pressure on the various rolls than would otherwise be required. This results in less wear on the mechanism and facilitates the proper maintenance thereof.

The inventon may of course be applied to roller grinding mills having more than three rolls in which case the back roll, that is the roll forming the rear portion of the feed hopper is driven at a speed in excess of double the peripheral speed of the cooperating roll. In the case of such multiple roll mills the hydraulic adjustment above described may be applied to both end rolls in which event the intermediate rolls will be fioating, or by suitable modification may be applied to the intermediate rolls as well as to the end rolls.

Various changes and modifications may be made and the invention may be applied to various uses as will be understood by a person skilled in the art.

What is claimed is:

' 1. In a roller mill, a plurality of rolls, adjustable bearing means carrying said rolls in a series, means applying adjustable pressure to said bearing means for holding said rolls in pressure engagement, said last means comprising a cylinder containing liquid, a piston sliding therein and connected mechanically to exert pressure against said bearing means, means exerting adjustable pressure on said liquid in said cylinder, a liquid reservoir communicating with said cylinder, a port connecting said reservoir with said cylinder, and means opening said port in response to an adjustment adapted to reduce the liquid pressure in said cylinder.

2. In a roller mill, a plurality of rolls, adjustable hearing means carrying said rolls in a series, means applying adjustable pressure to said bearing means for holding said rolls in pressure engagement, said last means comprising a cylinder containing liquid, a piston sliding therein and connected mechanically to exert pressure against said hearing means, means exerting adjustable pressure on said liquid in said cylinder, a liquid reservoir communicating with said cylinder, a port connecting said reservoir with said cylinder positioned to be closed by said piston when in normal operating position and to be opened upon retraction of said piston in said cylinder.

3. In a roller mill, a plurality of rolls, adjustable hearing means carrying said rolls in a series, means applying adjustable pressure to said bearing means for holding said rolls in pressure engagement, said last means comprising a cylinder containing liquid, a piston sliding in said cylinder and connected to apply pressure to said bearing means, adjustable means mounting said cylinder for sliding movement with respect to said piston and adapted to vary the liquid pressure in said cylinder, a liquid reservoir connected with said cylinder, a port connecting said reservoir to said cylinder and positioned to be closed normally by said piston and to be opened in response to retraction in said cylinder in a direction to reduce the liquid pressure on said piston, whereby the cylinder is recharged with said liquid from said reservoir.

4. In a roller mill, a plurality of rolls, adjustable bearing means. carrying said rolls in a series, means applying 6 adjustable pressure to said bearing means for holding said tion to reduce the liquid pressure therein, for thereby rerolls in pressure engagement, said last means comprising a charging said cylinder and reservoir. cylinder containing liquid, a piston sliding therein and connected to apply pressure to said bearing means, a threaded Ref re ces Cltefl m the file 0f thls patent member connected to adjust said cylinder axially for in- 5 UNITED STATES PATENTS creasing or decreasing the liquid pressure exerted on said piston, a liquid pressure gauge connected to said cylinder g i g ,3 to register the liquid pressure therein, a liquid reservoir 2224330 fi n5 1940 connected to said cylinder, a port connecting said cylinder 2249364 gg z 5 1941 and positioned normally to be closed by said piston and 10 2,331,172 Butler fly Oct. 1943 to be opened upon retraction of said cylinder in a direc- 

